It's the first time in almost 600 years that a Pope has stepped down from the position. And Pope Benedict XVI says he's he's fully aware of the gravity of the move.

The Pope was last seen in public only yesterday, he was also tweeting Sunday.

And Popes are allowed to resign. A handful have done so in the past but generally, they don't. It's thought that's to avoid possible divisions and instability if there are two Popes around, even if one has retired.

The Vatican says a new Pope is expected to be elected by the end of March.